Assessment of carotid artery dose in the treatment of nasopharyngeal cancer with IMRT versus conventional radiotherapy.
OBJECTIVE
To determine the radiation dose to the carotid artery in nasopharyngeal cancer patients treated with intensity-modulated radiotherapy (IMRT) and to compare it to the dose delivered by a conventional three-field (3F) technique.


METHODS
Sixteen patients with nasopharyngeal cancer who were treated at UCSF with IMRT were selected for this analysis. 3F plans were reconstructed for comparison. The carotid arteries were retrospectively contoured, and the dose received by each of the 32 carotid arteries was determined for both IMRT and 3F plans. A subset of 8 patients with N0/N1 nodal disease was selected for IMRT replanning using additional constraints to reduce the dose to the arteries.


RESULTS
Using the standard prescription doses for IMRT and 3F plans, the dose delivered to 95% of the tumor volume was significantly higher in the IMRT plans, reflecting the greater conformality of this technique. The median mean dose to the carotid arteries was 65.7Gy with IMRT vs. 58.4Gy with 3F (p<0.001). After the application of dose constraints to the carotid arteries, it was possible to reduce the mean carotid dose to 54Gy in the IMRT replans.


CONCLUSIONS
IMRT achieves a higher tumoricidal dose and superior clinical target volume coverage, but results in an increase in the carotid artery dose as compared to conventional 3F technique. With careful IMRT planning, it is possible to constrain the carotid dose for a subset of patients with low-risk neck disease. Further study is necessary to quantify the long-term clinical impact of this intervention.
Vitolo
Viviana
V
Department of Radiation Oncology, University of California-San Francisco, San Francisco, CA 94143-1708, USA.
Millender
Laura E
LE
Quivey
Jeanne M
JM
Yom
Sue S
SS
Schechter
Naomi R
NR
Jereczek-Fossa
Barbara A
BA
Milani
Franco
F
Orecchia
Roberto
R
Xia
Ping
P
D002339:Carotid Arteries / Q000528:radiation effects*; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated